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Open Roads Forum  >  Towing

 > Wiring questions

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jdrphs

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Posted: 02/26/12 07:01am Link  |  Print  |  Notify Moderator

Got a Q about rigging my 4 pin to a 7 pin. I can handle the wiring fine, I am very good at 12v. I do, however, have limited knowledge of what a few the wires actually do for the trailer. (reverse just for lights, or something to do with the brakes?) I am going to install my own brake controller, which seems simple as I have alreay looked at the install instructions for the prodigy units. Also thinking about the primus. Anyone got that one? I see its a simple 12v, ground, blue wire to the back of the truck, wire to the brake switch. simple. Question is, do I really need to hook up the 12v pin on the harness, and will in need the reverse light hookup? I will have electric brakes, and the TT will have a battery obviously. I could handle this, but dont want to do the extra work if all i need is turns, running lights, ground and brakes actually going through the harness. I found a great adapter from Hopkins that will tie into my existing 4-pin, with pig tails for the extra ground, 12v, trailer brake and reverse. Also comes with a slick mount that should fit right onto my existing hitch. Thanks all.

midnightsadie

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Posted: 02/26/12 07:17am Link  |  Print  |  Notify Moderator

well you,d be all wired up if you needed to tow some other trailer. I
CA Traveler

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Posted: 02/26/12 07:56am Link  |  Print  |  Notify Moderator

In the long run you would be more flexible with a 7 pin plug on the truck. Mine has 2 larger connectors for larger wire for gnd and 12V. Fuse the 12V at the TV battery and the trailer battery.


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badboy368

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Posted: 02/26/12 07:23am Link  |  Print  |  Notify Moderator

one thing to be aware of is the size of the wires in your 4 pin. you need to have a large enough wire to carry the brake power to the trailer. too small a wire will not carry enough amps. same with a ground, it needs to be large enough. this is a case where size does matter.


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eHoefler

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Posted: 02/26/12 07:44am Link  |  Print  |  Notify Moderator

The 12v pin will help keep the battery charged on the trailer. If you keep the refrigerator running, it will need 12v for its operation. Granted a fully charged house battery will keep it going for quite some time. If you are in freezing conditions, you may want to run the furnace while you are on the road, it will consume a lot of power to run, a charge line from the tow vehicle will help keep the battery up. The reverse light is kind of a convenience thing. I have back up lights on my fifth wheel, really handy if you have to back up at night. Also, if you ever tow a trailer with surge brakes, disc brakes in particular, the reverse light lead activates a brake lock out solenoid on the brake actuator. It keeps you from applying the surge brakes while backing up.


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Posted: 02/26/12 07:48am Link  |  Print  |  Notify Moderator

12V is likely not necessary with a good charged battery and short trips. But it does keep the battery charged for refer, brakes and any other usage like when stopped or perhaps leaving a light on while towing.

I also find little value in the reverse light.

2112

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Posted: 02/26/12 08:14am Link  |  Print  |  Notify Moderator

I mounted and wired 2 backup lights on my TT bumper so we can see when backing into a site at night. Not saying you need it but it does make things easier. I want to wire them to 12V through a switch to use them at the camp site if needed.


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jasult

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Posted: 02/26/12 08:50am Link  |  Print  |  Notify Moderator

here is good site for help. Look on right side of page for wire diagram
you will see a 7 way diagram for truck side and trailer side

click here


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jdrphs

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Posted: 02/26/12 09:08am Link  |  Print  |  Notify Moderator

Wow, you guys are a huge help. I see the value in charging the battery, but is it really needed. I do not plan to tow at night, so the reverse lights are out as a needed item to start. What size wire do I need for the run from the brake controller to the 7 pin? I have a 2005 chevy colorado, and from what I understand there is not plug and play option. I plan to grab the switch ingnition power under the steering column as I always did with remote starts, that way my brake controller will turn off with the ignition.
Can I run like 10 or 12ga power directly from the battery like hooking up and amplifier, with an inline fuse ( the run for the 7 pin power, not brake controller) or do I need some sort of isolator so the truck is not pulling from the trailer battery? I love wiring stuff up, can't wait to start this when it warms up
I am getting the hopkins 47185. Looks like the light wires will plug directly into my 4 flat, and I will have only the other 4 to worry about, ground, 12v, Brake, and reverse. Sound like I am on the right path?
Will I be happy with a primus IQ. I am very sensitive to light while driving, and have heard the prodigy's blue display is quite bright and not dimmable. I hate when I install a radio that is bright and won't dim.

mobilefleet

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Posted: 02/26/12 08:32am Link  |  Print  |  Notify Moderator

both of these are plug and play in most cases now.....you already have the 4 way to 7 way adapter, and you can also buy a harness (unless you already have one) that will plug directly into your fuse box if your vehicle is around 2004 or newer. No more cutting and splicing wires for brake controller. You don't mention what your tow vehicle is, so this may not help you. When we bought our 05 Tahoe there was actually a wire harness in the glove box that was plug and play for a brake controller, it was included in the owners manual packet.

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